feat: add document pipeline, ReAct agent, and knowledge core services

Document Pipeline (Team A):
- LibrarianService: document storage with filesystem backend, metadata
  persistence, child document hierarchy, collection management
- ChunkingService: recursive character text splitter with configurable
  chunk size/overlap, FlowProcessor pattern
- KnowledgeExtractService: combined relationship + definition extraction
  using prompt service and LLM, emits RDF triples and entity contexts
- KnowledgeCoreService: knowledge core CRUD with streaming export and
  flow-based loading

ReAct Agent (Team B):
- StreamingReActParser: state machine for parsing LLM output into
  Thought/Action/ActionInput/FinalAnswer sections
- Three MVP tools: KnowledgeQuery (GraphRAG), DocumentQuery (DocRAG),
  TriplesQuery with RequestResponse clients
- AgentService FlowProcessor with ReAct loop, tool execution, and
  streaming chunk responses (thought/observation/answer)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ts/packages/flow/src/librarian/collection-manager.ts

@@ -0,0 +1,73 @@
+/**
+ * Collection manager — in-memory CRUD for document collections.
+ *
+ * Used by LibrarianService to manage collections per-user.
+ * MVP: purely in-memory, no persistence (state is persisted
+ * via the parent LibrarianService JSON snapshot).
+ */
+
+export interface CollectionEntry {
+  user: string;
+  collection: string;
+  name: string;
+  description: string;
+  tags: string[];
+}
+
+export class CollectionManager {
+  /** keyed by `${user}:${collection}` */
+  private collections = new Map<string, CollectionEntry>();
+
+  private key(user: string, collection: string): string {
+    return `${user}:${collection}`;
+  }
+
+  listCollections(user: string): CollectionEntry[] {
+    const result: CollectionEntry[] = [];
+    for (const entry of this.collections.values()) {
+      if (entry.user === user) {
+        result.push(entry);
+      }
+    }
+    return result;
+  }
+
+  getCollection(user: string, collection: string): CollectionEntry | undefined {
+    return this.collections.get(this.key(user, collection));
+  }
+
+  updateCollection(
+    user: string,
+    collection: string,
+    name: string,
+    description: string,
+    tags: string[],
+  ): CollectionEntry {
+    const entry: CollectionEntry = { user, collection, name, description, tags };
+    this.collections.set(this.key(user, collection), entry);
+    return entry;
+  }
+
+  deleteCollection(user: string, collection: string): boolean {
+    return this.collections.delete(this.key(user, collection));
+  }
+
+  ensureCollectionExists(user: string, collection: string): CollectionEntry {
+    const existing = this.getCollection(user, collection);
+    if (existing) return existing;
+    return this.updateCollection(user, collection, collection, "", []);
+  }
+
+  /** Serialize to a plain array for JSON persistence. */
+  toJSON(): CollectionEntry[] {
+    return [...this.collections.values()];
+  }
+
+  /** Restore from a serialized array. */
+  loadFromJSON(entries: CollectionEntry[]): void {
+    this.collections.clear();
+    for (const entry of entries) {
+      this.collections.set(this.key(entry.user, entry.collection), entry);
+    }
+  }
+}